This invention concerns a specialty bag construction and method of manufacturing the same. In particular, the bag wall has a number of venting bands for the proper venting of certain stored perishable items.
Bulk bags are commonly used to store and transport many agricultural products. Many such products, especially those easily perishable ones, require the bag to be properly vented to prevent the build up of excessive moisture with ensuing growth of mold and deterioration of the content. Furthermore, these bags are usually non-reusable due to sanitation concern. Thus, these ventable bags need to be produced in high volume, having a specifiable degree of venting yet with very low cost. One common way to achieve this is to weave in a set of venting bands of specified width and density with a flat loom. However, the associated post operation involves, after cutting the panel to size, folding and sewing of two lines to form the bag. Additionally, the flat loom machine is quite an expensive investment. Thus, the overall production cost of the bag can be undesirably high.
The present invention consists of a method which inexpensively and efficiently manufactures such ventable bags in high volume with a specifiable range of design of venting bands. Thus, the bag itself is also encompassed by the present invention.
The bag is a traditional one having a cylindrical body panel with one end of the panel sown closed to form the storage cavity. The other end of the cylindrical body panel is left open for communication with the interior of the bag. However, the cylindrical body panel of the bag comprises a specified number and location of venting bands along the direction of the cylindrical axis. Furthermore, the width of the said venting bands is also specifiable by design.
The method of manufacturing the bag starts with the tubular weaving of yams of proper materials with a circular loom whereby an elongated tubular structure is formed with woven warp and weft strands. The direction of the warp strands is parallel to the tubular axis whereas the direction of the weft strands is perpendicular to the tubular axis.
However, around the periphery of a concentration ring of said circular loom a number of mechanical expansion blocks are disposed at the proper location replacing the otherwise warp strands to be fed thus woven into said cylindrical body panel of the bag. For convenience, these locations are to be called band locations. As there is an absence of warp strands at each such band location, the resulting woven wall structure of the said band consists of only weft strands. Without the interlocking power from the missing warp strands, the flexing weft strands within said band create substantially larger air gaps in between than otherwise possible with the presence of interlocking warp strands. These air gaps within said bands thus form the desired venting structure for the bag. Therefore, emerging from said circular loom with the adaptation of the invention embodiment is a woven tubular structure wherein a number of venting bands parallel to the tubular axis are built in wherever said invention embodiment is disposed along the circumferential periphery of the tube. It is also important to remark that, as part of the function of the circular loom, said emerging woven tubular structure is actually flattened into a continuous belt form and wound into a roll for easiness of subsequent handling.
The tubular structure is sectioned off along a set of lines with predetermined spacing to form a set of tubular segments, each tubular segment having the desired set of venting bands extending axially from a first open end to a second open end. For convenience, the first open end of the said tubular structure is to be called the top opening and the second open end of the said tubular structure is to be called the bottom opening.
The bottom opening of the said tubular structure is now sewn closed along the direction perpendicular to the tubular axis. The top opening of the said tubular structure is left open forming the desired bag opening.
Thus, a storage bag having a cylindrical body panel is described wherein a desired set of venting bands extending axially is built in on the body panel. Additionally, an inexpensive and efficient method is described herein for the manufacturing of such ventable bags in high volume. Furthermore, said method of manufacturing embodies the adaptation of a set of simple mechanical elements onto an existing circular loom.
Other features, objects and advantages of the present invention will become apparent with reference to the following drawings and associated descriptions.